Parenting skills interventions have been shown to help prevent substance use and mental health disorders (NCR/IOM, 2009; Sandler et al., 2011). Unfortunately, the public health potential of these interventions is severely limited because few parents engage in them. The proposed research is a randomized effectiveness trial of a theory-based engagement package that has been found in an efficacy trial to nearly double the rate of initiation into an evidence-based parenting intervention compared to a control engagement condition (48% vs. 25%). Engagement package effects on initiation were mediated by changes in targeted motivational constructs (i.e., parental attitudes, perceived obstacles). The engagement package increased participation for high-need families by reducing disparities in engagement for single-parent and English-Speaking Mexican American families, who have been less likely to participate in parenting interventions, and by increasing engagement among parents of children experiencing behavior problems (BPs) in the classroom. The proposed trial tests the effects of this engagement package when implemented under natural service delivery conditions through a partnership with a large, public school district. Parents of kindergarten and 1st grade students (N = 1,350) will be interviewed at three time-points: pre-test, post-engagement, and post-parenting program. Data will also be collected from teachers, group leaders and objective raters. The project has four specific aims: 1. Compare the effectiveness of engagement package components using a dismantling design. Kindergarten and 1st grade classrooms will be randomly assigned to one of five conditions: 1) standard brochure; 2) brochure + family testimonial flyer; 3) brochure + teacher endorsement; 4) brochure + group leader engagement call (GLEC); 5) brochure + testimonial flyer + teacher endorsement + GLEC. 2. Examine socio-cultural variables (family structure and SES; parent ethnicity and primary language) and baseline child BPs as moderators of the effects of engagement condition on enrollment and initiation. 3. Examine whether amount of exposure and implementation variability of the motivational engagement components accounts for variability in enrollment and initiation rates within each condition. 4. Test a mediation model of the effects of the engagement package on parenting and child outcomes. Compared to the brochure condition, families from classrooms randomly assigned to the full engagement package are expected to show higher initiation rates and consequently greater session attendance in an evidence-based parenting intervention, the Triple P Positive Parenting Program (Sanders, 2008); which in turn, should lead to greater improvements from pre- to post-Triple P on risk factors for substance abuse (i.e., child BPs, parenting dysfunction) and child mental health problems. Such a finding would suggest that this motivationally-enhanced engagement package could substantially increase the public health impact of evidence-based parenting interventions that prevent substance use and mental health disorders.